8086CPU has a 20-bit address bus, which can transmit 20-bit addresses and achieve 1MB addressing capability.
8086CPU is a 16-bit structure, and the address for one-time processing, transmission, and temporary storage inside is 16 bits.
Judging from the internal structure of the 8086CPU, if the address is simply sent from the inside, it can only send out a 16-bit address, and the displayed addressing capability is only 64KB.
8086CPU uses a method of combining two 16-bit addresses internally to form a 20-bit physical address.